I've just been playing it, dunno if the xpa one is a repack of the p2p dump thats going around, theres also some kind of an R4 patched version on Asian sites but anyway.

Out of the j-pop song list theres was a couple i was familiar with. An old one by Bump of Chicken "Tentai Kansoku" (which was also on the Daigasso Band Bros expansion pack, Ai Otsuka's latest single "PEACH" and The Blue Hearts "Linda Linda", which was in Osu! Tatakae! Ouendan.